Germanium diodes- the definitive answer

Frequent question abouts LED and other types of diodes.

Germanium diodes- the definitive answer

Postby darkstar » 08 Aug 2011, 18:43

1)Ok so Ive searched round the not and ive found half people saying how much smoother they are than silicons and half people saying these are the harshest and LEDs are the smoothest. who is right?!?!?!?!?

2)i know they clip earlier. i have also found some people saying they have more distortion than silicons and some people saying less. who is right?!?!?
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Re: Germanium diodes- the definitive answer

Postby culturejam » 08 Aug 2011, 18:47

Moved.

And now I'll answer:

I think it depends on the circuit. But usually LEDs are a little harsher, at least to my ears. Sometimes that works well, and sometimes not.

Germanium clips more than silicon or LED. So it's going to naturally produce more compression and it will sound more "distorted". It's also going to result in less output volume.
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Re: Germanium diodes- the definitive answer

Postby DrNomis » 08 Aug 2011, 18:54

darkstar wrote:1)Ok so Ive searched round the not and ive found half people saying how much smoother they are than silicons and half people saying these are the harshest and LEDs are the smoothest. who is right?!?!?!?!?

2)i know they clip earlier. i have also found some people saying they have more distortion than silicons and some people saying less. who is right?!?!?



It really depends on where the diodes are connected in the circuit, if you have two Ge diodes as back-to-back clippers with an op-amp, they should clip smoothly and gradually, here's a couple of pics of diode clipping as seen on an oscilloscope,note the difference in the sharpness of the clipping:
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Re: Germanium diodes- the definitive answer

Postby Duckman » 08 Aug 2011, 20:00

Tested on the same circuit, I tend to hear from a very triangular wave and lower volume (Ge) through a intermediate between triangular and square with an acceptable volume (Si) up to a nearly square with the volume boosted (LED ).
Very subjective at the waveform, I know, but I always have this image in mind. :scratch:
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Re: Germanium diodes- the definitive answer

Postby darkstar » 09 Aug 2011, 11:57

awesome thanks guys
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Re: Germanium diodes- the definitive answer

Postby RnFR » 09 Aug 2011, 13:55

I'm sure this is already on the forum somewhere, but-

Ge diodes have the lowest forward voltage drop(Vf)(.3V vs. .6V for Si), which means with the same input signal, the diodes will conduct sooner and you will hear more distortion, and less output. you can remedy this by putting them in series. they also have the roundest conduction knee, which you can see in the smoother wave above. this makes them sound smoother than the others. LEDs have a very high voltage drop(depends on color), letting the circuit sound louder, but they also have a harsher knee. this all usually just comes down to personal preference. one of the fun things a beginner can do is buy a bunch of different types of diodes and fool around with them, mixing and matching til your heart's content.
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Re: Germanium diodes- the definitive answer

Postby asatbluesboy » 09 Aug 2011, 15:44

LED will be the harshest of all, and Ge has the less output (as already pointed out by many). Si vs LED is pretty much RAT vs Turbo RAT.
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Re: Germanium diodes- the definitive answer

Postby emakris » 09 Aug 2011, 17:17

DrNomis wrote:
darkstar wrote:1)Ok so Ive searched round the not and ive found half people saying how much smoother they are than silicons and half people saying these are the harshest and LEDs are the smoothest. who is right?!?!?!?!?

2)i know they clip earlier. i have also found some people saying they have more distortion than silicons and some people saying less. who is right?!?!?



It really depends on where the diodes are connected in the circuit, if you have two Ge diodes as back-to-back clippers with an op-amp, they should clip smoothly and gradually, here's a couple of pics of diode clipping as seen on an oscilloscope,note the difference in the sharpness of the clipping:


DrNomis, what is your circuit setup? What kind of signal are you running through them in these pictures?
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Re: Germanium diodes- the definitive answer

Postby GuitarlCarl » 09 Aug 2011, 17:40

Trade secret from china dude... then we gooped it.
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Re: Germanium diodes- the definitive answer

Postby DrNomis » 09 Aug 2011, 18:07

emakris wrote:
DrNomis wrote:
darkstar wrote:1)Ok so Ive searched round the not and ive found half people saying how much smoother they are than silicons and half people saying these are the harshest and LEDs are the smoothest. who is right?!?!?!?!?

2)i know they clip earlier. i have also found some people saying they have more distortion than silicons and some people saying less. who is right?!?!?



It really depends on where the diodes are connected in the circuit, if you have two Ge diodes as back-to-back clippers with an op-amp, they should clip smoothly and gradually, here's a couple of pics of diode clipping as seen on an oscilloscope,note the difference in the sharpness of the clipping:


DrNomis, what is your circuit setup? What kind of signal are you running through them in these pictures?



It's actually a really simple setup, I just arranged the Silicon Diodes and Germanium Transistors (used as Diodes) as per the diagram below on my breadboard:

You might recognize the Diode Configuration as that used by Marshall in their JCM 800 and 900 Amps.

Note:As it says in the diagram, I set the signal generator to produce a 1kHz Sinewave , and adjusted the output till it caused the diodes to clip the signal-peaks.... :thumbsup
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Re: Germanium diodes- the definitive answer

Postby emakris » 09 Aug 2011, 18:46

DrNomis wrote:
emakris wrote:
DrNomis wrote:
darkstar wrote:1)Ok so Ive searched round the not and ive found half people saying how much smoother they are than silicons and half people saying these are the harshest and LEDs are the smoothest. who is right?!?!?!?!?

2)i know they clip earlier. i have also found some people saying they have more distortion than silicons and some people saying less. who is right?!?!?



It really depends on where the diodes are connected in the circuit, if you have two Ge diodes as back-to-back clippers with an op-amp, they should clip smoothly and gradually, here's a couple of pics of diode clipping as seen on an oscilloscope,note the difference in the sharpness of the clipping:


DrNomis, what is your circuit setup? What kind of signal are you running through them in these pictures?



It's actually a really simple setup, I just arranged the Silicon Diodes and Germanium Transistors (used as Diodes) as per the diagram below on my breadboard:

You might recognize the Diode Configuration as that used by Marshall in their JCM 800 and 900 Amps.

Note:As it says in the diagram, I set the signal generator to produce a 1kHz Sinewave , and adjusted the output till it caused the diodes to clip the signal-peaks.... :thumbsup


Drnomis, thank you. I honestly wasn't sure if you would answer and share with me of all people, and I'm glad you did. Again, thank you.
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Re: Germanium diodes- the definitive answer

Postby DrNomis » 09 Aug 2011, 19:03

emakris wrote:
DrNomis wrote:
emakris wrote:
DrNomis wrote:
darkstar wrote:1)Ok so Ive searched round the not and ive found half people saying how much smoother they are than silicons and half people saying these are the harshest and LEDs are the smoothest. who is right?!?!?!?!?

2)i know they clip earlier. i have also found some people saying they have more distortion than silicons and some people saying less. who is right?!?!?



It really depends on where the diodes are connected in the circuit, if you have two Ge diodes as back-to-back clippers with an op-amp, they should clip smoothly and gradually, here's a couple of pics of diode clipping as seen on an oscilloscope,note the difference in the sharpness of the clipping:


DrNomis, what is your circuit setup? What kind of signal are you running through them in these pictures?



It's actually a really simple setup, I just arranged the Silicon Diodes and Germanium Transistors (used as Diodes) as per the diagram below on my breadboard:

You might recognize the Diode Configuration as that used by Marshall in their JCM 800 and 900 Amps.

Note:As it says in the diagram, I set the signal generator to produce a 1kHz Sinewave , and adjusted the output till it caused the diodes to clip the signal-peaks.... :thumbsup


Drnomis, thank you. I honestly wasn't sure if you would answer and share with me of all people, and I'm glad you did. Again, thank you.



No worries, I'm only too happy to share with anyone, all circuit diagrams and other stuff I post is posted for the benefit of everyone here in freestompboxes.org, in the spirit of DIY..... :thumbsup
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Re: Germanium diodes- the definitive answer

Postby DrNomis » 09 Aug 2011, 19:46

There's also this screenshot of Led Clipping on my Oscilloscope, with the same breadboard setup as for the other two screenshots, except this time the diodes are Leds of course:
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Re: Germanium diodes- the definitive answer

Postby RnFR » 09 Aug 2011, 22:23

there are other things that go into the difference of Ge diodes vs. others as well. leakage and capacitance being two of them.
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Re: Germanium diodes- the definitive answer

Postby deltafred » 10 Aug 2011, 00:00

DrNomis wrote:There's also this screenshot of Led Clipping on my Oscilloscope, with the same breadboard setup as for the other two screenshots, except this time the diodes are Leds of course:


Are you sure you have the correct photo there, that looks awfully like a sine wave to me?
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Re: Germanium diodes- the definitive answer

Postby mictester » 10 Aug 2011, 00:07

RnFR wrote:there are other things that go into the difference of Ge diodes vs. others as well. leakage and capacitance being two of them.


The capacitance tends to only be a few pF, so won't have a significant effect at audio frequencies. However, leakage can have a significant effect, as can temperature (that's GERMANIUM Lance). There's also quite a wide spread in forward voltage drop against current with germanium diodes so asymmetry is often inherent!
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Re: Germanium diodes- the definitive answer

Postby DrNomis » 10 Aug 2011, 01:07

deltafred wrote:
DrNomis wrote:There's also this screenshot of Led Clipping on my Oscilloscope, with the same breadboard setup as for the other two screenshots, except this time the diodes are Leds of course:


Are you sure you have the correct photo there, that looks awfully like a sine wave to me?



Yes, it is, I had to turn-up the output level of the signal generator quite a bit to get the Leds to clip the signal as much as shown in the screenshot, the Leds were at full brightness when I took that screenshot pic(5 Red 5mm Leds were used)..... :thumbsup


Leds actually have a soft turn-on characteristic which is similar to Germanium diodes, except that the forward voltage drop for a Led is much greater than a Germanium diode, hence the reason why the signal still looks relatively Sinewave-like even at high signal levels...... :thumbsup
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Re: Germanium diodes- the definitive answer

Postby DrNomis » 10 Aug 2011, 01:31

I need to go see the people at Territory Housing for a couple of things today, when I get back home I'll breadboard a simple Op-Amp circuit with 2 back-to-back clipping diodes and post some new screenshots in this forum thread, so please stay tuned..... :thumbsup
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Re: Germanium diodes- the definitive answer

Postby Greg » 10 Aug 2011, 01:37

I say Germaniums tend to sound sound harsher.. even at the same clipping threshold.
What we see on a scope and what our ears perceive are 2 different things.
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Re: Germanium diodes- the definitive answer

Postby DrNomis » 10 Aug 2011, 01:49

Greg_G wrote:I say Germaniums tend to sound sound harsher.. even at the same clipping threshold.
What we see on a scope and what our ears perceive are 2 different things.



That's true, the Oscilloscope has a bandwidth that's quite a few orders of magnitude wider than the human ear, my Scope can go from DC to 20Mhz, a young healthy ear can go from 20hz to 20kHz, as we age we lose the high-end response of our ears naturally due to aging, or excessive loud noise exposure, what we see on a Scope screen is really a graph of Voltage versus Time, to see the individual harmonics, we need a Spectrum Analyser, wish I had one.... :hmmm:

It's interesting how our ears are able to hear the harmonics of a signal as a perceived Timbral-Colour.... :hmmm:
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